/* ===========================
   CSS Custom Properties (Design Tokens)
   =========================== */
:root {
    /* Colors */
    --color-primary: #2563eb;
    --color-primary-hover: #1d4ed8;
    --color-secondary: #64748b;
    --color-background: #ffffff;
    --color-surface: #f8fafc;
    --color-text-primary: #0f172a;
    --color-text-muted: #64748b;
    --color-border: #e2e8f0;
    --color-overlay-bg: rgba(15, 23, 42, 0.9);
    --color-tag-bg: #e0e7ff;
    --color-tag-text: #3730a3;
    --color-tag-active-bg: #2563eb;
    --color-tag-active-text: #ffffff;
    
    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    --font-size-sm: 14px;
    --font-size-base: 16px;
    --font-size-lg: 18px;
    --font-size-xl: 24px;
    --font-size-2xl: 32px;
    --line-height-tight: 1.25;
    --line-height-normal: 1.5;
    --line-height-relaxed: 1.75;
    
    /* Spacing */
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;
    --spacing-2xl: 48px;
    
    /* Layout */
    --container-max-width: 1200px;
    --card-min-width: 280px;
    --border-radius: 8px;
    --border-radius-lg: 12px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 200ms ease-in-out;
    --transition-slow: 300ms ease-in-out;
}

/* ===========================
   Reset & Base Styles
   =========================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: var(--line-height-normal);
    color: var(--color-text-primary);
    background-color: var(--color-background);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ===========================
   Header
   =========================== */
header {
    background-color: var(--color-background);
    border-bottom: 1px solid var(--color-border);
    padding: var(--spacing-lg) var(--spacing-md);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-lg);
    max-width: var(--container-max-width);
    margin: 0 auto;
}

.profile-photo {
    width: 120px;
    height: 120px;
    border-radius: 50%;
    object-fit: cover;
    flex-shrink: 0;
}

.header-nav-section {
    display: flex;
    flex-direction: column;
    align-items: center;
}

header h1 {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-md);
    text-align: center;
}

/* Tab Navigation */
nav[role="tablist"] {
    display: flex;
    justify-content: center;
    gap: var(--spacing-sm);
    position: relative;
}

button[role="tab"] {
    background: none;
    border: none;
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    font-weight: 500;
    color: var(--color-text-muted);
    padding: var(--spacing-sm) var(--spacing-lg);
    cursor: pointer;
    border-bottom: 2px solid transparent;
    transition: color var(--transition-base), border-color var(--transition-base);
    min-height: 44px;
    min-width: 44px;
}

button[role="tab"]:hover {
    color: var(--color-text-primary);
}

button[role="tab"]:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

button[role="tab"][aria-selected="true"] {
    color: var(--color-primary);
    border-bottom-color: var(--color-primary);
}

/* ===========================
   Main Content
   =========================== */
main {
    max-width: var(--container-max-width);
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-md);
}

/* Hide inactive tab panels */
section[role="tabpanel"][hidden] {
    display: none;
}

/* ===========================
   Projects View
   =========================== */
.intro-text {
    font-size: var(--font-size-lg);
    color: var(--color-text-muted);
    line-height: var(--line-height-relaxed);
    text-align: center;
    margin-bottom: var(--spacing-lg);
}

hr {
    border: none;
    border-top: 1px solid var(--color-border);
    margin: var(--spacing-xl) 0;
}

/* Filter Controls */
.filter-controls {
    margin-bottom: var(--spacing-xl);
}

.tag-filters {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
    justify-content: center;
}

.search-controls {
    display: flex;
    gap: var(--spacing-sm);
    max-width: 700px;
    margin: 0 auto;
    align-items: center;
}

.tag-chip {
    background-color: var(--color-tag-bg);
    color: var(--color-tag-text);
    border: none;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius);
    font-size: var(--font-size-sm);
    font-weight: 500;
    cursor: pointer;
    transition: background-color var(--transition-base), color var(--transition-base), transform var(--transition-fast);
    min-height: 44px;
    min-width: 44px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

.tag-chip:hover {
    transform: translateY(-1px);
    background-color: var(--color-primary-hover);
    color: var(--color-tag-active-text);
}

.tag-chip:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

.tag-chip.active {
    background-color: var(--color-tag-active-bg);
    color: var(--color-tag-active-text);
}

/* Search Bar */
.search-bar {
    flex: 1;
    padding: var(--spacing-md);
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    background-color: var(--color-surface);
    transition: border-color var(--transition-base), box-shadow var(--transition-base);
}

.search-bar:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.search-bar::placeholder {
    color: var(--color-text-muted);
}

/* Clear Filters Button */
.clear-filters-btn {
    background-color: var(--color-surface);
    color: var(--color-text-primary);
    border: 1px solid var(--color-border);
    padding: var(--spacing-md) var(--spacing-lg);
    border-radius: var(--border-radius);
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    font-weight: 500;
    cursor: pointer;
    transition: background-color var(--transition-base), border-color var(--transition-base);
    min-height: 44px;
    white-space: nowrap;
}

.clear-filters-btn:hover {
    background-color: var(--color-background);
    border-color: var(--color-primary);
    color: var(--color-primary);
}

.clear-filters-btn:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* Projects Grid */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(var(--card-min-width), 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

/* Prevent single card from being too wide */
.card-grid > .project-card:only-child {
    max-width: 500px;
}

/* Project Cards */
.project-card {
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-lg);
    overflow: hidden;
    transition: transform var(--transition-base), box-shadow var(--transition-base);
    cursor: pointer;
    position: relative;
    display: flex;
    flex-direction: column;
    z-index: 1;
}

.project-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.project-card:focus-within {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* Card Screenshot Container */
.project-card-screenshot-container {
    width: 100%;
    aspect-ratio: 16 / 9;
    overflow: hidden;
    background-color: var(--color-border);
}

.project-card-screenshot {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
}

/* Card Content (below screenshot) */
.project-card-content {
    padding: var(--spacing-md);
    flex: 1;
    display: flex;
    flex-direction: column;
    z-index: 2;
    position: relative;
}

.project-card-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-xs);
}

.project-card-date {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-sm);
}

.project-card-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
    margin-top: auto;
}

.project-card-tag {
    background-color: var(--color-tag-bg);
    color: var(--color-tag-text);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius);
    font-size: var(--font-size-sm);
    font-weight: 500;
}

/* Card Overlay */
.project-card-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--color-overlay-bg);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: var(--spacing-lg);
    opacity: 0;
    pointer-events: none;
    transition: opacity var(--transition-slow);
    z-index: 3;
}

/* Desktop: Show overlay on hover and focus */
@media (hover: hover) {
    .project-card:hover .project-card-overlay,
    .project-card:focus-within .project-card-overlay {
        opacity: 1;
        pointer-events: auto;
    }
}

/* Mobile: Show overlay when card has active class */
.project-card.card--active .project-card-overlay {
    opacity: 1;
    pointer-events: auto;
}

.project-card-description {
    color: #ffffff;
    font-size: var(--font-size-base);
    line-height: var(--line-height-relaxed);
    text-align: center;
    margin-bottom: var(--spacing-lg);
    max-width: 90%;
}

.project-card-buttons {
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
    justify-content: center;
}

.project-card-button {
    background-color: var(--color-primary);
    color: #ffffff;
    border: none;
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--border-radius);
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    font-weight: 500;
    cursor: pointer;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 44px;
    min-width: 120px;
    transition: background-color var(--transition-base), transform var(--transition-fast);
}

.project-card-button:hover {
    background-color: var(--color-primary-hover);
    transform: translateY(-1px);
}

.project-card-button:focus {
    outline: 2px solid #ffffff;
    outline-offset: 2px;
}

.project-card-button.secondary {
    background-color: rgba(255, 255, 255, 0.2);
    backdrop-filter: blur(8px);
    border: 1px solid rgba(255, 255, 255, 0.3);
}

.project-card-button.secondary:hover {
    background-color: rgba(255, 255, 255, 0.3);
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: var(--spacing-2xl) var(--spacing-md);
    color: var(--color-text-muted);
    grid-column: 1 / -1;
}

.empty-state-message {
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-md);
}

.empty-state-action {
    background-color: var(--color-primary);
    color: #ffffff;
    border: none;
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--border-radius);
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    font-weight: 500;
    cursor: pointer;
    min-height: 44px;
    min-width: 44px;
    transition: background-color var(--transition-base);
}

.empty-state-action:hover {
    background-color: var(--color-primary-hover);
}

.empty-state-action:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* ===========================
   About View
   =========================== */
.about-content {
    max-width: 800px;
    margin: 0 auto;
}

.bio {
    font-size: var(--font-size-lg);
    line-height: var(--line-height-relaxed);
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-xl);
    text-align: center;
}

/* Profile Cards */
.profile-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.profile-card {
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-xl);
    text-decoration: none;
    color: var(--color-text-primary);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 150px;
    transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
    cursor: pointer;
}

.profile-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--color-primary);
}

.profile-card:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

.profile-card .icon {
    width: 48px;
    height: 48px;
    margin-bottom: var(--spacing-md);
    background-color: var(--color-primary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.profile-card .label {
    font-size: var(--font-size-lg);
    font-weight: 600;
    text-align: center;
}

/* ===========================
   Footer
   =========================== */
footer {
    border-top: 1px solid var(--color-border);
    padding: var(--spacing-lg) var(--spacing-md);
    margin-top: var(--spacing-2xl);
    text-align: center;
}

footer p {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

footer a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color var(--transition-base);
    padding: var(--spacing-xs);
    border-radius: 2px;
}

footer a:hover {
    color: var(--color-primary-hover);
    text-decoration: underline;
}

footer a:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* ===========================
   Responsive Design
   =========================== */

/* Mobile: Base styles above (mobile-first) */

/* Tablet: 641px and above */
@media (min-width: 641px) {
    header {
        padding: var(--spacing-xl) var(--spacing-lg);
    }
    
    header h1 {
        font-size: var(--font-size-2xl);
    }
    
    main {
        padding: var(--spacing-2xl) var(--spacing-lg);
    }
    
    .card-grid {
        grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    }
    
    .profile-cards {
        grid-template-columns: repeat(3, 1fr);
    }
}

/* Desktop: 1025px and above */
@media (min-width: 1025px) {
    header h1 {
        margin-bottom: var(--spacing-lg);
    }
    
    .card-grid {
        grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    }
    
    .intro-text {
        font-size: var(--font-size-xl);
    }
}

/* ===========================
   Accessibility & Print
   =========================== */

/* Reduced motion for users who prefer it */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* High contrast mode support */
@media (prefers-contrast: high) {
    :root {
        --color-border: #000000;
        --color-text-muted: #000000;
    }
}

/* Print styles */
@media print {
    header {
        position: static;
    }
    
    .project-card-overlay,
    .filter-controls,
    nav[role="tablist"] {
        display: none !important;
    }
    
    .project-card {
        break-inside: avoid;
    }
}